Gas turbines generally include a rotor with a number of circumferentially spaced blades or buckets mounted in adjacent positions extending radially about the periphery of a rotor wheel or disk. The buckets generally include an airfoil, a platform, a shank, a dovetail, and other elements. The dovetail is positional about the rotor and secured therein, generally by being slidably received in a complimentary configured recess in the rotor disk. The airfoils project into the gas path so as to convert the kinetic energy of the gas into rotational mechanical energy.
Each airfoil typically includes a convex side and a concave side. Likewise, the airfoil platform typically includes a leading edge and a trailing edge extending between the convex side and the concave side. A pair of generally axially spaced support ledges may be positioned on the convex side of the bucket. Likewise, an undercut may be positioned within the bucket platform from the leading edge to the trailing edge along the convex side on the other end. The undercut may include an angled surface that may extend the full axial length of the bucket.
During engine operation, vibrations may be introduced into the turbine buckets that can cause premature failure of the buckets if the vibrations are not adequately dissipated. In order to improve the high cycle fatigue life of a turbine bucket, vibration dampers are typically provided below the platforms to frictionally dissipate vibratory energy and reduce the corresponding amplitude of vibration during operation. The amount of vibration energy that is removed by the vibration damper is a function of the dynamic weight of the vibration damper and the reaction loads.
Although these known dampers may be largely adequate during typical operations, there is a desire to improve overall damper effectiveness. Prior attempts to accomplish damping of vibrations have included round damper pins, sheet metal flat dampers, or complex wedge shaped dampers. Often the true damper performance of these types of dampers is not known until the first engine test. At that time, the damper pocket geometry in the buckets is locked in by hard tooling. If the damper does not perform as expected, then an expensive tooling rework is required. Accordingly, there is desire to eliminate one or more of these aforementioned problems.